Mineral pigments are added to paper with the aim of improving its optical and printing properties. The colloidal behavior of calcium carbonate filler shows a dependence on the quality of water used in suspensions, presence of dissolved and colloidal substances and type of polymer used as a retention aid. The role of the retention aids is to attach colloidal particles, such as fines and mineral pigments, to pulp fibers before or during the paper is made. Two very different single-component retention aids were utilized in calcium carbonate fillers destabilization and deposition on fibers. Cationic polyethylenimine destabilized or facilitated deposition of the filler on fibers by a charge neutralization mechanism while cationic polyacrylamide flocculated or deposited the filler on fibers via a bridging mechanism. / In the presence of anionic dissolved and colloidal substances, the amount of cationic polyacrylamide had to be increased in order to achieve the same degree of pigment flocculation. The reason for the increase was due to the fact that the cationic polyacrylamide formed a polyelectrolyte complex with the anionic substances, namely sulfonated kraft lignin. The reaction between cationic polyacrylamide and lignin was found to be nearly stoichiometric. Low molecular weight cationic polyacrylamide formed mostly colloidal complexes while high molecular weight cationic polyacrylamide formed predominantly coacervate complexes; this was mainly due to differences in characteristic times of lignin association with the cationic polyacrylamide, clustering of polyacrylamide molecules and reconformation of polymer chains. / The performance of two-component retention aid systems consisting of a cationic polyacrylamide and anionic microparticles were evaluated by deposition of calcium carbonate filler on pulp fibers. Kaolin clay and bentonite were used to heteroflocculate polyacrylamide-covered surfaces of the fibers and pigment. Due to their inability to delaminate, kaolin clay and acid-treated montmorillonite showed no effect of calcium carbonate filler deposition. After cation exchange with sodium-rich solutions, which caused the montmorillonite to delaminate, the montmorillonite flocculation efficiency considerably improved. Kaolin clay neither delaminated after the cation exchange nor improved calcium carbonate deposition. Bentonite was found to completely delaminate when using polyacrylamide-treated fibers. When added to a suspension of fibers, filler and cationic polyacrylamide, bentonite was found to be in a form of stacks containing on average four platelets. / An alternative way to paper filling with pigment was tested on stationary sheets and on slow and fast Fourdrinier pilot paper machines. Using a secondary headbox on the pilot paper machines, a high degree of loading (above 30%) could be achieved using positive clay or calcium carbonate fillers. However, the fillers lowered the paper strength as they interfered with the fiber-fiber bonding in a similar fashion found in conventionally filled papers.

This study focuses on understanding the photochemical reactions that occur between ultraviolet stabilizers and lignin during irradiation in order to further comprehend the photo-protection mechanisms of these stabilizers during brightness reversion. The stabilizers chosen for study included a variety of ultraviolet absorbers (UVAs), in addition to a hindered nitroxide free radical (4-hydroxy-TEMPO). Irradiated samples were analyzed using quantitative 31P NMR, in addition to a technique known as 'Derivatization Followed by Reductive Cleavage'. / Benzophenone-based UVAs have been shown to be actively involved in photochemical reactions with lignin during irradiation, while benzotriazole-based UVAs are comparatively photostable under identical irradiation techniques. All additive combinations were found to inhibit the formation of carboxylic acids and photochemical condensation reactions in lignin; however, the joint application of 2,4-DHB and 4-hydroxy-TEMPO demonstrated synergistic inhibition of these reactions. / All additive combinations were shown to impede the formation of catechol structures and to retard the cleavage of lignin beta-arylether groups during irradiation. The combined use of Tinuvin 1130 and 4-hydroxy-TEMPO provided the most efficient inhibition of these reactions. These results provide insight into the excellent photoyellowing inhibition provided by this additive combination when applied onto mechanical pulps.

Researchers have linked resin and fatty acids (RFAs) to acute toxicity, especially in thermomechanical and chemithermomechanical pulp and paper mill effluents. Thus, the measurement of total RFAs may be a rapid, inexpensive alternative to standard methods of toxicity monitoring, such as 96-hour rainbow trout testing. Current procedures for the analysis of RFAs typically involve solvent extraction and concentration, derivatization, and analysis by GC, HPLC, or TLC. These procedures are far too expensive, complicated, and time-consuming for implementation at mill sites. / This thesis reports the development of a rapid, colourimetric assay based on the dye methylene blue (MB) for the quantification of resin and fatty acids in pulp and paper mill effluents. This MB assay uses the complexation of the cationic organic dye molecule to the carboxylic acid groups of RFAs to form a measurable chromophore. The electrically neutral, blue-coloured complexes are then extracted into a poorly polar organic solvent, dichloromethane. The measured absorbance at 655 nm is directly related to the total RFA concentration in the effluent sample. / The methylene blue assay is inexpensive and simple to use. It has a method detection limit of 0.589 mg/L total RFA. There are good correlations between the results obtained using the methylene blue assay and a well-established GC assay, and between RFA concentrations measured by the MB assay and acute toxicity measured by Microtox. The assay is sufficiently simple and rapid to be practical for routine in-mill monitoring.

Borate can be a potential candidate to protect building envelope components from biodegradation as it has low toxicity and can penetrate wood without pressure treatment, even in the refractory species commonly used in construction industries as structural components. In this research, wood moisture content, grain direction, formulation and species that affect the diffusion of borate in refractory species were investigated. Two highly concentrated formulations were applied and a novel approach (borate bandage) was used to keep the preservative on the surface and enhance the diffusion by reducing surface drying. From ANOVA test for different diffusion periods and depths of penetration, it was found that grain directions and moisture content are significant factors. A mould test was performed, the diffusion co-efficients were calculated and some recommendations were made about the quantity required to protect a specific volume of wood considering the distance moved by diffusion and volume treated in different directions.

Borate can be a potential candidate to protect building envelope components from biodegradation as it has low toxicity and can penetrate wood without pressure treatment, even in the refractory species commonly used in construction industries as structural components. In this research, wood moisture content, grain direction, formulation and species that affect the diffusion of borate in refractory species were investigated. Two highly concentrated formulations were applied and a novel approach (borate bandage) was used to keep the preservative on the surface and enhance the diffusion by reducing surface drying. From ANOVA test for different diffusion periods and depths of penetration, it was found that grain directions and moisture content are significant factors. A mould test was performed, the diffusion co-efficients were calculated and some recommendations were made about the quantity required to protect a specific volume of wood considering the distance moved by diffusion and volume treated in different directions.

Column flotation as a concept was introduced approximately 90 years ago at Inspiration Copper Co., Arizona, with the first successful installation occurring at Les Mines Gaspe, Quebec, in 1981. Column flotation has since been applied to many other industries including deinking of recycled paper. / The research is a comparison of industrial bubble generating devices in a pilot and laboratory column using water/Dowfroth and pulp sampled on-line from a local deinking plant. The pilot column tested combinations of 6, 4 and 2 stainless steel (ss) porous spargers, and filter cloth and jetting sparger; the lab column used a single ss porous sparger. Long term tests on the pilot column were also done to evaluate maintenance issues. / Trends from the water/Dowfroth tests were used to predict results using pulp. Six ss spargers outperformed the other spargers in all cases. The performance of the lab column sparger matched 4 spargers, with the filter cloth performing marginally better than the jetting sparger or 2 spargers. / Gas holdup (Eg) and bubble surface area flux (Sb) gave good correlation with ink removal with all spargers failing within a narrow range. Surface area flux is suggested over Eg unless bubble diameter or superficial gas velocity are indeterminable. Sb > 100 s-1 gave ink removals equal to the plant Voith cells. An Sb below 40 s-1 gave zero ink removal. The lab and pilot column followed slightly different trends which was attributed to column diameter (i.e., wall effects). / The ss and filter cloth spargers present long term maintenance issues due to plugging. The performance of the 6 ss spargers decreased more quickly than any other during the long term tests, attributed to lower air velocities per pore.

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